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What are rods and cones in the retina of an eye?

Rods are rod shaped cells present in the retina are sensitive to dim light. They are most important for vision in dim light.

Cones are cone shaped cells present in the retina are sensitive to bright light. These photoreceptor cells are responsible for color vision.

Name the part of the eye:

(a) which controls the amount of light entering the eye.

(b) which converges light rays to form the image.

(d) which carries the image to brain.

(e) which changes the curvature (or thickness) of eye-lens to focus objects lying at various distances.

Name the cells on the retina of an eye:

(a) which are sensitive to bright light.

(b) which are sensitive to dim light.

Name any one defect of the eye. How is it corrected?

What is cataract? How can the vision of a person having cataract be restored?